FE 537 Plot scale Oregon State University FE
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FE 537 Plot scale Oregon State University
FE 537 What this section will address Plot scale Hillslope scale Catchment scale Oregon State University
Outline FE 537 u From core to plot n Quick review of flow and transport in porous media n Problems with the notion of linear upscaling of soil core information u Plot scale changes with depth n Some experimental data u Preferential flow changes with depth n Some experimental data u Summary n Plot scale conceptualization and how this links to the hillslope scale Oregon State University
FE 537 From core to plot Oregon State University
FE 537 Our so-called subgrid parameterization Jan Hopmans, UC Davis Oregon State University
FE 537 The steps How does measurement uncertainty in these steps affect estimation of K(h)? Sherlock et al. , 2000 Oregon State University
FE 537 Oregon State University What’s important conceptually
FE 537 Source: Mike O’Kane Oregon State University How we define this quantitatively
FE 537 Source: Mike O’Kane Oregon State University Just to be clear
So for unsaturated conductivity… FE 537 Hydraulic conductivity mm/hr 1000 Water is the conducting medium! 100 10 1 0 Oregon State University -100 -200 Water potential cm. H 2 O
FE 537 Photo by Jim Kirchner Oregon State University But wait, structure trumps texture! Intact field soil very different to admixtures of sand/silt/clay
FE 537 Oregon State University Preferential flow
FE 537 If Darcy were alive today… Merde! Oregon State University
FE 537 Oregon State University Two common strategies to deal with this Source: Brent Clothier, WISPAS Newsletter 2008
Darcy revisited FE 537 u It’s not that Darcy does not apply (almost all of the time) u It’s just that a different physics kicks in during brief windows in time n Days or weeks of Darcian bordom, punctuated by all (macropore) hell breaking loose! n Think of it as a struggle between the Newtonian vs Darwinian world views u read John Harte’s 2002 paper in Physics Today (on merging the Newtonian and Darwinian world views) Oregon State University
The plot scale paradox FE 537 surface, topsoil matrix u While large pore space makes up only a small percent of the total porosity, they control almost all the flow at or near saturation soil pipes n. Almost all our theory is for the matrix n. We‘ve learned about as much as we ever will for pure textural mixtures and re-packed field soilshighly soil base permeable layers Peter Kienzler, ETH Zurich Oregon State University
Not a new idea FE 537 The curse of preferential flow 1898 - Some 104 years ago Oregon State University Courtesy Brent Clothier
FE 537 Plot scale changes with depth Oregon State University
At depth FE 537 Evaporation Transpiration Infiltration Lateral flow Deep percolation Oregon State University Photo: Markus Weiler UBC
Hydrology’s most basic equation FE 537 n. Zr ds/dt = I(s, t) - E(s, t) - L(s, t) Where: n is porosity, Z is soil depth, s is the relative soil moisture content, I is infiltration, E is evaporation and L is leakage Rodriguez-Iturbe (2000, WRR) notes that “although apparently simple, this presents serious challenges when the terms in the RHS are considered dependent on the state s. Oregon State University
Changes with depth FE 537 Oregon State University one of your benchmark papers
FE 537 Some data from the same site Data from WS 10, HJA, Kevin Mc. Guire Oregon State University
FE 537 Ksat changes with depth! Saturated hydraulic conductivity with exponential curve fits. The dashed lines indicate the envelope for most data observations. Data from WS 10, HJA, Kevin Mc. Guire Oregon State University
FE 537 Drainable porosity u Drainable porosity = saturated water content – water content at field capacity u Change in drainable porosity will directly alter the depth function of drainable storage in the soil u Relates to ground water table fluctuations Data from WS 10, HJA, Kevin Mc. Guire Oregon State University
FE 537 Oregon State University Why such changes with depth?
. . and for many nutrients FE 537 Also distinct depth distributions Oregon State University Data from forest soils (Hagedorn et al. , 2001)
FE 537 The preferential flow – matrix link Soil matrix changes with depth conspire with vertical preferential flow: u. Drainable porosity u. Bulk density z u. Hydraulic conductivity u. Pore size distribution Oregon State University ? Peter Kienzler, ETH Zurich
A now common mechanism FE 537 Storm Rainfall Sd 18 O = -10 o/oo dq/d. Z y<0 d 18 O = -4. 5 o/oo Oregon State University u New water bypass flow to depth u Transient saturation at soil-bedrock interface u Lateral pipeflow of old water due to limited storage and head u Bedrock surface control of mobile water u Rapid recession after rainfall ends u Important coupling of unsaturated and transient saturated zones. d 18 O = -5 o/oo
FE 537 Why this is important for runoff generation? Water cannot enter the pipe drain when it is placed above the level of the water table (i. e. water will not flow from a position of low potential in the soil to a position of higher potential). Water will only enter the drain when it is placed within the saturated zone (below the water table) and if there is sufficient hydraulic head. (Mc. Laren and Cameron, 1994) Oregon State University Remember this when we move to the hillslope scale…
FE 537 Kitihara-san’s Lab at FFPRI in Japan R Oregon State University
FE 537 More detail on preferential flow changes with depth Oregon State University
FE 537 It’s network-like and it’s ubiquitous A network of connected macropores and fissures that rapidly transmits water & solutes through the rootzone Oregon State University Courtesy Brent Clothier
A quick case study to illustrate this FE 537 Sprinkling experiments on undisturbed soils: the work of Weiler and Naef electric linear actuator nozzles covered dry plot wind protection gutter tensiometer and TDR probes Oregon State University overland flow measurement pump and control
FE 537 Oregon State University Sprinkling and dye tracing experiments Markus Weiler, Freiburg University
Mapping FE 537 0 High rainfall intensity Dry soil 8 cm pth 50 cm De Horizontal dye pattern Depth 15 cm Legend unstained stones macropores 57 cm Stained areas with low concentration medium concentration Oregon State University Markus Weiler, Freiburg University high concentration
FE 537 Soil water content and preferential flow Soil water content measurement Vertical dye pattern Depth (m) Flow process 1. 0 Legend Oregon State University Surface initiation Stained areas with (water repellency) High rainfall intensity unstained low concentration stones medium concentration Dry soil macropores Markus Weiler, Freiburg University high concentration High interaction (permeable matrix)
An animation FE 537 High rainfall intensity Depth (m) Dry soil Dye pattern Water content change 1. 0 Oregon State University Markus Weiler, Freiburg University
FE 537 Matric potential and preferential flow Recall Weyman, Burt and others from your reader…. Matric potential measurement Vertical dye pattern Flow process Depth (m) 1. 0 Subsurface initiation Legend (saturated matrix) Stained areas with unstained low concentration medium concentration stones Low interaction high concentration macropores (saturated matrix) Oregon State University Markus Weiler, Freiburg University
Other sites FE 537 High rainfall intensity Depth (m) Dry soil Dye pattern Water content change 1. 0 Oregon State University Markus Weiler, Freiburg University
Other sites FE 537 Low rainfall intensity Depth (m) Dry soil Dye pattern Water content change 1. 0 Oregon State University Markus Weiler, Freiburg University
Other sites FE 537 Low rainfall intensity Depth (m) Wet soil Dye pattern Water content change 1. 0 Oregon State University Markus Weiler, Freiburg University
FE 537 Infiltration in macroporous soils Macropore Flow Initiation Water supply to the macropores Interaction Water transfer between macropores and the surrounding soil matrix Oregon State University Markus Weiler, Freiburg University
How do macropores influence runoff processes? FE 537 Activated macropore rapid infiltration Runoff reaction Storage Oregon State University Fast Subsurface Flow Markus Weiler, Freiburg University Overland Flow
FE 537 The preferential flow – matrix link revisited Soil matrix changes with depth conspire with vertical preferential flow: u. Drainable porosity u. Bulk density z u. Hydraulic conductivity u. Pore size distribution Oregon State University ? Peter Kienzler, ETH Zurich
A now common mechanism FE 537 Storm Rainfall Sd 18 O = -10 o/oo dq/d. Z y<0 d 18 O = -4. 5 o/oo Oregon State University u New water bypass flow to depth u Transient saturation at soil-bedrock interface u Lateral pipeflow of old water due to limited storage and head u Bedrock surface control of mobile water u Rapid recession after rainfall ends u Important coupling of unsaturated and transient saturated zones. d 18 O = -5 o/oo
Implications for modeling FE 537 Traditional conceptual runoff models Unsaturated storage Saturated storage What undergraduate textbooks will state Oregon State University
Implications for modeling FE 537 A process prerequisite Unsaturated storage Saturated storage Oregon State University
FE 537 The use of qualitative, conceptual models can overcome the shortcomings of quantitative models. Conceptual models consider the sum interaction of all processes, even if not known, that result in a particular phenomenon (Pilkey and Pilkey-Jarvis, 2007). Oregon State University
FE 537 Weiler and Mc. D, 2004 Jo. H Oregon State University One example
FE 537 Conclusions Oregon State University
FE 537 Peter Kienzler, ETH Zurich Oregon State University This section u From core to plot n Quick review of flow and transport in porous media n Problems with the notion of linear upscaling of soil core information u Plot scale changes with depth n Some experimental data u Preferential flow changes with depth n Some experimental data u Summary n Plot scale conceptualization and how this links to the hillslope scale
Next section From vertical to lateral flow FE 537 Q Q Qs Often an impeding horizon or soil-bedrock contact z Saturated vertical hydraulic conductivity Oregon State University % Saturation Downward percolation Lateral subsurface flow
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